Process and apparatus for producing oxygen



Jul 13, 1937. E. P. MCCREERY 2,086,567

PROCESS AND APPARATUS FOR PRODUCING OXYGEN Filed Jan. 20, 1956 2 Sheets-Sheet 1 I I! I IN V EN TOR.

2 A TTORNE Y July 13, 1937. E. P. MCCREERY- 2,086,567

PROCESS AND APPARATUS FOR PRODUCING OXYGEN Filed Jan. 20, 1936 2 Sheets-Sheet 2 -fi..: w WM INVENTOR.

/ 7 Wig/59w? BY flea/ad ATTORNEY Patented July 13, 1937 PATENT OFFICE PROCESS AND APPARATUS FOR PRODUC- ING OXYGEN Esley P. McCreery, Stockton, Calif., assignor of twenty per cent to P. W. Stamps, Berkeley,

and twenty per cent to David B.

Stockton, Calif.

Stamps,

Application January 20, 1936, Serial No. 59,916

10 Claims. (01. 62-175.5)

This invention relates to a process and apparatus for separating the various gases of which air iscomprised and principally in recovering the oxygen gas therefrom.

Prior to my invention, various processes and apparatus have been devised for separating the gases of the air to recover the oxygen, nitrogen and other gaseous content thereof. The apparatus for practicing these prior processes have been expensive both to produce and to maintain due to their complicity and due to the high pressures under which they operated.

It is the principal object of my present invention to provide an improved, simple and efficient 15 process of separating the gaseous contents of the air and recovering the same, and to provide an eflicient apparatus for practicing that process, which apparatus is simple in construction, inexpensive to produce and to operate, and which operates at comparatively low pressures.

In practicing my invention, the air is compressed to a suitable pressure and the moisture is eliminated therefrom and it is then expanded to reduce its temperature. An exchange of heat is then effected between the compressed air supply and the expanded cold air to reduce the temperature of the former until the temperature thereof is so lowered that when expanded it liquefies. The liquid air is then agitated to separate the colder gases therefrom and an exchange of heat between these gases and the compressed air supply is effected to lower the temperature of the latter. likewise, an exchange of heat betweeh the oxygen and the compressed air supply is effected, both to purify the oxygen by boiling off the impure gases therein and to reduce the temperature of the air supply; By the' above described means of cooling the incoming compressed air, I am enabled .to eliminate the use of such 4 devices as Vaporizers, air expanders and ice machines in apparatus for separating and recovering oxygen from the air.

My improved process is exemplified in the following description and my apparatus for practicing it is illustrated by way of example in the accompanying drawings, in which:

Fig. 1 is a schematic view of my improved apparatus showing parts thereof in central vertical section to more clearly disclose certain features of construction.

Fig. 2 is a transverse sectional view taken transversely through the heat exchanging chamber of the machine.

Fig. 3 is an enlarged fragmentary view in central vertical section through the heat exchang ing chamber showing the manner in which the coils are connected to the manifolds and headers.

Fig. 4 is a transverse sectional view through the expansion chamber taken on line IV--IV of Fig. 1.

Fig. 5 is an enlarged view in central vertical section through the expansion chamber.

Fig. 6 is a transverse sectional view taken through the rectifying chamber.

My apparatus as illustrated in the drawings comprises a compressor 2, potash tubes 3 and a liquefaction unit 9. The latter includes an elongated cylindrical drum Ill suitably constructed to withstand the internal pressures built up therein. This drum in is provided with a closed upper head H and a closed lower head [2. The interior of this drum encloses what I prefer to term a heat exchanging chamber M, an expansion chamber I5, 2. rectifying and separating chamber l6 and a collecting and purifying chamber l'l. It will be noticed from the drawings that the heat exchanging chamber It is uppermost and that the expansion chamber I5 is interposed between it and the separating chamber l6, while the collecting chamber is disposed below the separating or rectifying chamber. All of these chambers as illustrated are in direct communication with each other.

Arranged concentrically about the drum I0 is an outer casin I 8 which is of a diameter considerably larger than the drum l0. sulat-ing material I9 is disposed in the annular space between the outer casing I8 and the drum I!) to prevent heat exchange between the drum Ill and the atmosphere. It will be noticed that the outer casing I3 is provided with head members 20 at opposite ends which are spaced from the head members H and iii of the drum ID so that; the insulation will extend about the ends of the drum ill for the purpose described.

Arranged within the heat exchanging chamber It are a plurality of air intake coils 2| and oxygen gas exhaust coils 22. The latter are disposed within the air intake coils 2i as will be hereinafter described.

Referring to Figs. 2 and 3, it will be seen that each air intake coil 2| is a double-wound coil. That is to say, commencing at its center both. ends are wound in opposite directions to form a pancake type of coil consisting of two layers as illustrated, so that the air or gas passing into one end will travel into the outer convolution of one layer of the coil; thence in the same direction to the smallest convolution of that layer; and thence into the smallestlaconvolution of the second layer Suitable inand outwardly discharging from the outer convolution of that layer through the end in communication'therewith.

One end of each air intake coil is connected with and in communication with an air intake manifold 23 arranged vertically within the insulation between the drum Ill and the outer casing IS. The other end of each coil is connected to a header 24 which is in efiect a manifold and which is preferably arranged between the casing I8 and the drum ID at a point diametrically opposite the air intake manifold 113;, so that the air will travel from the. air intake manifold 23 through the coil and thence into the header 24 or vice versa as will be described.

Arranged within each air intake coil 2! is an oxygen exhaust coil 22. That is to say, I prefer that the air intake coil be of say half inch tubing, while the oxygen exhaust coil arranged therein be of say quarter inch tubing, the two being wound together as illustrated.

One end of the oxygen exhaust coil 22 is connected to an oxygen exhaust manifold 25, while the other end of each oxygen exhaust coil 22 is connected with an exhautt header 2% which is likewise a manifold in effect. It will be noticed from Fig- 3 that the ends of the-oxygen exhaust coils extend diametrically through the air intake manifold 23 and the header 2%, there being, however, no communication therebetween.

I prefer that the coils be arranged in batteries of eight. That is to say, that at a'point just below the first eight coils the air intake manifold 23 is blanked off so that the incoming air entering the upper end of the air intake manifold 23 will pass through the first eight coils simultaneously and then into the header 2d. The header it is blanked off at a point below the sixteenth coil so that the incoming air entering the same from the first eight coils will pass into the second eight coils and thence back. into the intake manifold 23. The intake manifold is again blanked off at a point below the twenty-fourth coil so that the air passing back into the manifold 23 through the second eight coils will travel through the third eight coils back into the header 241. This system of arranging the coils in batteries of eight is carried onthroughout the entire length of the manifold 23 and header 2% in'the same manner so that the incoming air will follow a circuitous path throughout eight coils successively from the top to the bottom of the heat exchanging chamber M.

I prefer that there be forty-eight of these coils, although a greater or lesser number may be used, depending upon the size of the machine and coils. The arrangement of the coils is such that the last eight coils will discharge into the intake-manifold 23 so that the air may pass from the lower end of this manifold into a feeder pipe 21.

The same system of arranging the oxygen exhaust coils 22 is employed in connection with the oxygen exhaust manifold 25 and the header 2% so that the exhausted oxygen will passthrough a series of eight coils throughout the length of the heat exchanging chamber It, and ultimately discharge through an oxygen discharge pipe 28 conlower end of the intake manifold '23 into the feeder pipe 21. Likewise, the oxygen delivered to the lower end of the exhaust manifold 25 will pass through the oxygen exhaust coils 22 throughout with a helical boiling coil 29. From the upper end of this boiling coil 29 the pipe 21 extends to and is connected with an expansion valve 30.

The expansion valve 30 is most clearly illustrated in Fig. 5, and referring to this figure, it will be seen that it comprises a body 3!! having a valve chamber 32 therein which is in communication with the feeder pipe 21. At one end of this valve chamber the body if is formed with a restricted valve port 33 controlled by a needle valve 34!. The cross-sectional area of this port 33 is considerably less than the'cross-sectional area of a nozzle tube 35 with which it communicates. Therefore, when the valve is open, the air discharging through the port 33 into the nozzle tubing 35 will expand so that its temperature will lower. I prefer to term this the first stage of expansion. At the end of the nozzle tubing 35 is a nozzle 36 which comprises two semi-cylindrical nozzle tips 37, both connected with the end of the nozzle tubing 35. The nozzle tips 37 are arranged in opposition to each other, and at a spaced distance apart, which distance I prefer to be approximately one-half inch, so that when the air discharges through these nozzle tips 37, the streams will impinge so that the air will be violently agitated as further lower its temperature.

When the air at this point is of a temperature sumciently low to cause it to liquefy, the liquid will lower into the separating or rectifying chamber it. Arranged in this chamber is a series of bafies or trays 39, which in this instance I prefer to be thirty-six in number. These trays are most clearly illustrated in Figs. 5 and 6 and comprise a disk at having a central opening ti formed therein, over which is disposed, at a spaced distance therefrom, a disk-like plate 62 so that the liquid will be caused to travel in a tortuous path downwardly through the separating chamber l6 into the collecting chamber i1.

Due to the tortuous path which the liquid air assumes in travelling downwardly through the separating chamber it, the colder or more volatile gases will be liberated and will travel upwardly. That is to say, nitrogen gas and other impurities in gas form will pass upwardly, while the oxygen, which will remain in liquid form, will lower into the collecting chamber N. This is due to the fact that the nitrogen and the gases other than the oxygen are colder and lighter'and revert from a liquid to a gas more rapidly than oxygen. Thus, the nitrogen and other gases will pass upwardly into the heat exchanging chamber I4 and between the coils and discharge through a discharge pipe 43 at the top of the drum l0.

It will be noticed that a tube 44, the ends of which have been blanked off, is disposed within the center of the coils 2| so that the nitrogen and other gases travelling upwardly through the chamber M must pass between the convolutions of the coils themselves. The impingement of this gas, which will be at 196 C. below, on these coils will naturally cause an exchange of heat between the coils and the gas, further lowering the temperature of the incoming air.

The oxygen in liquid form will, as previously described, collect in the chamber H in which the coil 29 is disposed. As previously stated, the incoming air travels through this coil before it reaches the expansion valve 30. Consequently, the temperature of this coil will be higher than the temperature of the liquid oxygen and will cause the same to boil, which agitation will cause further liberation of the nitrogen or other gases remaining in the liquid oxygen.

In the operation of the apparatus and carrying out the process, the compressor 2 receives the air from the atmosphere and compresses it at the commencement of operation of the machine to 1500 pounds per cubic inch. This compressed air is delivered from the compressor through the potash tubes 3 to the upper end of the air intake manifold 23. The potash tubes, as previously described, eliminate the moisture from the air, which elimination is necessary to prevent this moisture from freezing in the machine and rendering the same inoperative.

The air delivered to the upper end of the intake manifold 23 passes through the air intake coils 2| and discharges from the lower end of the intake manifold 23 into the delivery pipe 21, from whence it travels through the coil 29 and the pipe 21 to the expansion valve 30.

I desire to call attention to the fact that the incoming air passing through the air intake coils 2| travels first inwardly of the coil and then outwardly thereof, reversing its direction of flow. This is important in that it retards the velocity of the air flow, allowing the cooling gases passing through the oxygen exhaust coils within the coils 2| and the gases passing around the exterior of the coils 2| within the heat exchanging chamber a sufficient length of time to chill the incoming air by the exchange of heat therewith.

-,The three stages of expansion previously described greatly reduces the temperature of the air. This cold air, which will not be sufficiently low in temperature to liquefy, will pass upwardly through the coils and commence chilling the same, thereby efiecting an exchange of heat between the outgoing cold air and the incoming warm air. Thus, the temperature of the air in the expansion chamber I5 will gradually lower until it reaches approximately -196 C., at which time it will commence to liquefy. As it liquefies, it will drop into the separating chamber I6 where it will assume a tortuous path due to the provision of the battles or trays 39. This, as previously described, agitates the liquid so as to liberate the nitrogen and other gases which are colder and lighter than the oxygen. These gases will pass upwardly to effect an exchange of heat with the coils 2| to maintain the incoming air at a low temperature. The liquid oxygen will lower into the collecting chamber l1, and when the gas pressure within the drum l0 reaches a suilicient point, the oxygen will be forced from the bottom of the collecting chamber I! through the discharge pipe 45 upwardly into the discharge manifold 25, and thence through the oxygen discharge coils 22 to the discharge pipe 28 connected with the top of the exhaust header 26.

In commencing the operation of the machine, I prefer that the air be compressed to 1500 pounds per cubic inch, and the coils such as I have shown and described herein enable approximately two hundred feet of air per minute to be delivered to the machine.

I find in actual practice that the machine will commence producing oxygen within six hours, at which time the air leaving the lower end of the manifold 23 and discharging into the feeder pipe 21 will be at approximately 80 C. below. This, plus the three stages of expansion at the expansion valve 30 and the exchange of heat between the contents of the agitating chamber I1 and the coil 29, will so lower the temperature of the air, that when it is expanded in the expansion chamber l5, it will be 196 C. and will liquefy. After the apparatus is in production, the working pressure is dropped to 600 pounds, which I find sufiicient.

It should be stated that the liquid oxygen gas discharging upwardly through the oxygen discharge coils 22 to the discharge pipe 28, while leaving the collecting chamber I! at approximately 184 C. below, discharges into the pipe 28 at approximately 68 F. above. Thus, by effecting an exchange of heat between the incoming air and the exhausted oxygen and the exhausted nitrogen and other impure gases in the manner which I have here disclosed, I am enabled to eliminate Vaporizers and other mechanical ice machines present in prior apparatus for producing oxygen.

I wish to point out the fact that there are no moving parts in my apparatus other than the compressor. Consequently, the cost of manufacturing the apparatus will be low and repairs and adjustments and maintenance costs will be practically eliminated.

I have also found in actual practice that my apparatus need not be defrosted as often as prior machines. Consequently, the same will be more efficient in operation.

The oxygen produced in actual practice in a machine in which the drum I0 is approximately twelve inches in diameter and twelve feet long is twenty-eight cubic feet of oxygen per minute, the oxygen being 99.6% pure. Tests show that approximately seventy percent of the oxygen in the air delivered to the machine is recovered.

While I have described my process and apparatus in detail, it is obvious that various changes may be made in its construction by those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A liquefaction process of separating the gaseous contents of air which includes the step of compressing the air, the step of liquefying the air by expanding the same in a plurality of successive stages, agitating the air during one of said stages and effecting an exchange of heat between all of the components of the air so expanded and the compressed air prior to expansion to reduce the temperature of said compressed air.

2. A process of separating the gaseous contents of air which includes the step of compressing the air, the steps of liquefying the air by expanding the same and effecting an exchange of heat between the components of the air so expanded and the compressed air just previous to expansion, effecting the said expansion in a plurality of stages and violently agitating the air during at least one of said stages, and then rectifying the resultant liquid air to separate the components thereof.

3. A liquefaction process of separating the gaseous contents of air which includes the step of compressing the air, the steps of liquefying the compressed air by expanding the same in three successive stages, violently agitating the air during at least one of said stages and effecting an exchange of heat between all of the components of the air so expanded and. the compressed air just previous to expansion, rectifying the resultant liquid air to separate the more volatile gases therefrom, and then collecting the oxygen in liquid form and gasifying said oxygen by the said exchange of heat.

4. A liquefaction process of separating the gaseous contents of air which includes the step of compressing the air, the step of expanding the air in three successive stages and violently agitating the air during at'least one of said stages, the step of effecting an exchange of'heat between the expanded air and the compressed air just previous to expansion until the temperature of the expanded air lowers to the point of liquefaction, then rectifying the liquid air to separate the more volatile gases therefrom, effecting an exchange of heat between the said more volatile gases and the compressed air just prior to expansion, and effecting an exchange of heat between the remaining gas in liquid form and the compressed air just prior to expansion.

5. A liquefaction process of separating the gaseous contents of air which includes the steps of compressing the air, extracting the moisture from the compressed air, expanding the compressed air in three successive stages and agitating the air during at least one stage of expansion, effecting an exchange of heat between the air so expanded and the compressed air just previous to expansion until the temperature of the expanded air is sufficiently low to cause it to liquefy, rectifying the liquid to cause the components thereof other than oxygen to separate therefrom in gas form, effecting an exchange of heat between the said components and the compressed air just prior to its expansion, and effecting an exchange of heat between the oxygen and the compressed air just prior to expansion to reduce the temperature of the compressed air and gasify the oxygen and raise its temperature.

6. A liquefaction process of separating the gaseous contents of air which includes the step of compressing the air to a pressure not to exceed 1500 pounds, the step of expanding the air in a plurality of successive stages and violently agitating the air during at least one of said stages, the step of effecting an exchange of heat between the expanded air and the compressed air just previous to expansion until the temperature of the expanded air lowers to the point of liquefaction, then reducing the pressure of said compressed air to the point where the rate of liquefaction approximates the rate of rectification, then rectifying the liquid air to separate the more volatile gases therefrom, effecting an exchange of heat between the said more volatile gases and the compressed air just prior to expansion and efiecting an exchange of heat between the remaining gas in liquid form and the compressed air just prior to expansion to lower the temperature of the said compressed air and to raise the temperature of said remaining gas in liquid form to gasify it.

7. In an apparatus of the character described, air expansion valve means to which compressed air is to be delivered and capable of expanding the compressed air in a plurality of successive stages and including means to violently agitate the air during one of said stages, an expansion chamber into which the air enters during the final stage of expansion, a heat exchanging chamber above said expansion chamber and in direct communication therewith, a rectifying chamber below the expansion chamber and in direct communication therewith, a plurality of coils arranged in said heat exchanging chamber and through which the compressed air passes to said air expansion valve means, rectifying means in said rectifying chamber to rectify the more volatile gases from the oxygen when the air is liquefied and passes into said rectifying chamber, and means for bringing the oiwgen into a heat exchanging relation with the air passing through said coils to effect an exchange of heat therebetween. I

8. In an apparatus of the character described,- air expansion valve means to which compressed air is to be delivered, and capable of expanding the compressed air in a plurality of stages and including means to violently agitate the air during one of said stages, an expansion chamber into which the air enters during the final stage of expansion, a heat exchanging chamber above said expansion chamber and indirect communication therewith, a rectifying chamber below the said expansion chamber and in direct communication therewith, a-plurality of coils arranged in said heat exchanging chamber and through which the compressed air passes to said air expansion valve means, a rectifying means in said rectifying chamber to separate the more volatile gases from the oxygen when the air is liquefied and passes into said rectifying chamber, a plurality of coils arranged within the first-named coils and through which oxygen passes whereby an exchange of heat will be effected between the oxygen and the compressed air passing through said first-named coils.

9. In an apparatus of the character described, a vertical drum enclosing an expansion chamber,

a heat exchanging chamber directly above the expansion chamber and in direct communication therewith, a rectifying chamber directly below the expansion chamber and in direct communication therewith, an oxygen collecting chamber directly below the rectifying chamber and in direct communication therewith, air expansion valve means associated with the expansion chamber and capable of expandingthe compressed air delivered thereto in three successive stages and including means to violently agitate the air during one stage of expansion, a plurality of sets of coils arranged in superimposed relation within said heat exchanging chamber and through which setsof coils compressed air successively passes to said air expansion valve means, a plurality of oxygen exhaust coils arranged in sets complementary to the first-named coils, one oxygen coil being arranged within each of the firstnamed coils, said oxygen coils being connected with the'said collecting chamber.

10. In an apparatus of the character described, a compressor, a vertical cylindrical drum enclosing an expansionchamber, air expansion valve means connected with said compressor and associated with said chamber and capable of 'expanding the compressed air delivered thereto in a plurality of successive stages and including means to agitate the air during one of said stages and discharge it'into said chamber, a heat exchanging chamber arranged directly above the said expansion chamber and in direct communication therewith whereby cold gases in the expansion chamber may rise and pass through the heat expansion chamber, a plurality of air de-' livery coils arranged in said heat exchanging "chamber andforming a connection between said compressor and said air expansion valve means and through which the compressed air must pass prior to reaching said expansion valve means, a rectifying chamber within said drum and arranged directly below the expansion chamber andv in direct communication therewith, rectifyirig means, in said chamber to separate the components of the liquid air produced in the expansion chamber and enabling the more volatile gases in gas form to pass upwardly through the expansion chamber and heat exchanging chamber and effect an exchange of heat between said gases and said incoming air in the said coils, an oxygen collecting chamber below the rectifying chamber, a plurality of oxygen exhaust coils, one oxygen coil being arranged within each air delivery coil, a connection between said oxygen exhaust coils and said collecting chamber'whereby the pressure of the gases within said drum will cause oxygen in the collectingchamber to pass through said oxygen coils and discharge, and thereby effect an exchange of heat between said'oxygen and the air in said delivery coils to lower the temperature of the incoming compressed air and raise the temperature of the oxygen until it gasifies.

ESLEY P. MoCREERY. 

